1. Field of the Invention
This invention pertains to a hydraulically actuated friction clutch or brake for use in the kinematic arrangement of an automatic transmission.
2. Description of the Prior Art
In a hydraulically actuated friction clutch or friction brake of the type used in the kinematic arrangement of an automatic transmission, the hydraulic force applied by a piston to the friction disc, spacer plates and pressure plate is reacted during engagement of the friction element conventionally by a retention ring seated within a recess formed in the wall of a member, such as a hydraulic cylinder. The internal surface of the reacting member is formed with axially directed spline teeth driveably engaged by the pressure plate friction discs and spacer plates.
In a conventional arrangement of this type, the pressure plate contacts the retaining ring with a pressure that is distributed along the annular adjacent surface of the retaining ring and across the radial depth or width of the retaining ring. Because the force applied to the retaining ring is distributed over a surface and not concentrated radially along a line, an eccentricity between the application of the force and its reaction on the member produces an annularly distributed axial force and an annularly distributed bending moment through the thickness of the reacting member. The retaining ring and the recess in which it is fitted are located near the free end of the reacting member. This location of the bending moment near a free end of the reaction member increases the magnitude of bending stress developed in the member in comparison to the magnitude of bending stress that would result if the bending moment were applied more distant from the free end. Furthermore, the bending moment produces tension stress on the inner surface of the reacting member, which adds to the tension stress produced in the reacting member by the axial reaction force. The combination of the bending moment applied near the free end of the reacting member and the tension force developed in reaction to the application of hydraulic pressure applied by the piston can combine to produce premature failure of the reacting member.